Hair is a proteinaceous substrate containing protein chains connected by sulfur-sulfur cross-linkages from cystine. When hair is bleached or permed, the cystine disulfide bonds are cleaved, typically with sodium thioglycolate, sodium sulfite, or some other disulfide bond-cleaving agent. The hair is then put into a curled or straightened state, whichever is desired, and the disulfide bonds are then allowed to reform. New sulfur-sulfur cross-linkages between the protein chains are formed thus locking the hair into the new array. In practice, not all of the disulfide bonds reform. This cleavage of the sulfur-sulfur cross-linkages results in a weakening of the hair making it more susceptible to breakage during combing and brushing. In addition, because perming formulations are generally very alkaline, some amide linkages in the protein chains are also cleaved resulting in a further weakening of the hair. Currently, there is no cosmetically acceptable method of improving strength by imparting additional cross-linkages to hair. Moreover, both the strength of the hair and the combing properties of the hair are adversely affected by the perming/bleaching process. Conventional treatments to improve the combing properties include various conditioning agents. However, because these conditioning agents do not covalently bond to hair, their conditioning effects are removed by washing and must be repeatedly applied. Improved shine and gloss, UV protection, anti-stat properties, anti-microbial protection, color, as well as many other improvements, which are desirable to intact and/or damaged hair, all suffer from a lack of permanence on hair and must be continually replenished.
While there are many disclosures that describe compositions useful for modifying proteinaceous substrates, none of the disclosures describe compositions that are entirely satisfactory. None of the disclosures describe the preparation of water-soluble or water-dispersible reactive polyimido compounds that can be covalently and permanently bonded to a proteinaceous substrate. The present invention provides such improved water-soluble or water-dispersible polyimido compounds, many of which, upon reaction, revert to biodegradable and environmentally friendly compounds.